LED (Light Emitted Diode) are currently widely used in new lighting design. More and more traditional lighting devices are replaced with LED lighting devices for LED having low cost and high optical efficiency.
To achieve better optical effect, color temperature is playing a more and more important role. In some cases, the color temperature of a LED lighting apparatus is preferred to be kept at a desired color temperature. In some other cases, the color temperature of a LED lighting apparatus is preferred to be adjusted dynamically by users with manual control or under automatic control.
To achieve a desired color temperature, more than one types of LED devices may be used together to achieve a mixed optical parameter, e.g. color temperature. In past, more than one control circuits need to be prepared for each type of LED devices. But, such design usually involves higher cost and may cause some instable light output.
Therefore, it is preferred to design a better lighting apparatus with more stable output and lower manufacturing cost.